To extend the paralyzed fingers of a stroke victim with hemiplegia, we have proposed a low-dimensional control system for a robotic finger which can grasp an object between the robotic finger and the paralyzed human fingers. In this study, we newly propose an extra finger that can face multiple fingers with low-dimensional control. This can be realized by adding a rotational joint for moving the base of the robotic finger where it is controlled by the common low-dimensional synergy controller. Experimental results showed that the proposed extra finger could realize 33 grasping postures and 4 peg manipulation patterns.
